Furnace



C. L. IPSEN Oct. 30, 1934.

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FURNACE Filed lay 28. 1932 6 Sheets-Sheet 4 Piglo.

Inventor: Carl L.. Ipsen b5 maze/M His Attorneg.

Oct. 30, 1934.

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353 LEI/E175 ROLLERS \nven-tor: Carl L.. \psen His Attorneg.

Oct. 30, 1934.

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FURNACE Filed May 28, 1932 6 Sheets-Sheet 6 TROLLEY CARRIAGE HEATINGRESISTANCE Inventor: Carl L. \psen,

ma K His Attorneg.

Patented Oct. 30, 1934 UNITED STATES PATENT OFFICE FURNACE YorkApplication May 28, 1932, Serial No. 614,173

20 Claims.

Heating apparatus My invention relates to furnaces suitable for thetreatment of materials at high temperatures, more particularly tofurnaces for heating high carbon or alloy steel bars and the like, andhas for an object the provision of a furnace which is arranged to beoperated continuously in a manner to insure a uniform product. It iswell understood by those skilled in the art that steel bars of highcarbon content must be gradually brought up to the desired temperaturebefore quenching in order to prevent undue stresses within the steelbars. Furthermore, where a charge consisting of a, plurality of steelbars is to be raised to a relatively high predetermined temperature, itwill be seen that special provision must be made for the support of thebars during heating. When steel bars are heated to a temperature of 1500to 1600 degrees Fahrenheit, more or less, the metal tends to becomeplastic and if the bars are supported on a plurality of spaced supportsthe bars will sag between them. Furthermore, the supports themselveswill be deformed due to the high temperature and heavy load imposed uponthem by the charge of bars. This load is of considerable magnitudeinasmuch as it is contemplated by the present invention to provide anapparatus which will handle a plurality of steel bars of considerablelength and diameter; for example, steel bars long and 8" in diameter.Furthermore, while the bars are at standstill on the supports, coldspots exist between the bars and the supports. Due to these cold spotsand the consequent unequal heating of the bars and the supports thereresults unequal expansions of both the work and the supports whichexpansions cause further deformation of the bars and supports.

For the continuous operation of the furnace, it is important thatprovision be made to insure that successive charges are each brought tothe same temperature just preceding quenching. Otherwise, the propertiesof the several loads will vary and there will not be a uniformity ofproduct. In the quenching of long steel bars it is necessary to providesome means of insuring a uniform quenching throughout the length of thebars. If this is not done portions of each bar of metal may be harderand more brittle than other portions and as a result under the stress ofload there may be a failure of the bars due entirely to the uneventempering.

In carrying out my invention in one form thereof I provide a furnaceparticularly suitable for automatic operation so that successive chargesof work may be uniformly heated to a predetermined temperature andquenched so as to be uniform in character and properties. Morespecifically, I provide a charge-supporting roll table which extendsthroughout the length of a plurality of heating chambers and is arrangedto form a run-out table at one end of the furnace. The rollers of theroll table are-operated in synchronism with each other so that thecharges may be oscillated during the heating operation. The rollers,therefore, form the supporting means for the charge during heating andby oscillating the rollers the deformation of the charge and the rollersdue to the sagging of the metal and to the unequal expansion of themetal, is substantially, if not entirely, eliminated. By rotating therollers in a single direction the charges are caused to progress throughthe furnace. A charging mechanism is arranged at one side of the firstheating chamber, known as the preheat chamber, and has for its functionthe introduction of charges of work into the preheat chamber. After acharge arrives on the run-out table located at one end of the furnace, acrane is arranged to transport the charge to a quenching g0 bath. Thecrane is constructed so that the bars are supported in a horizontalplane. During the quenching operation the crane automatically raises andlowers the charge beneath the level of the quenching liquid, to causethe liquid to wash over the bars first in one direction and then in theother thereby insuring a uniform cooling of each bar throughout itslength as well as the uniform cooling of the several bars. The movementof the carriers of the crane and of the charge also introduces astirring action which is helpful in maintaining the quenching liquid ata more uniform temperature.

For a more complete understanding of my invention, reference should nowbe had to the drawings in which Fig. 1 schematically illustrat-es afurnace embodying my invention; Fig.

2 shows a complete layout chart of the several units of a furnaceembodying my invention in an improved form; Fig. 3 shows a plan view ofthe 10 charging mechanism, the preheat chamber and a fraction of thehigh-heat chamber of Fig. 2; Fig. 4 is a sectional elevation taken alongthe lines 4-4 of Fig. 3; Fig. 5 shows a plan view of a fraction of thehigh-heat chamber, the runout table, and a fraction of the quench tank;Fig. 6 shows an elevation of Fig. 5 taken on the line 6-6; Fig. 7 is anenlarged sectional elevation taken on line 7-7 of Fig. 3 showing thedetails of the charging mechanism in relation to the preheat chamber;Fig. 8 shows the charging mechanism in a position for inserting a chargeof material in the preheat chamber; Fig. 9 shows an enlarged sectionalelevation taken on the lines 9-9 of Fig. 3; Fig. 10 shows a sectionalelevation taken on the lines 1010 of Fig. 5; Figs. 11 and 12diagrammatically illustrate an improved form of an electrical controlsystem applied to my invention; Fig. 13 illustrates the relation ofFigs. 11 and 12 to each other, while Fig. 14 shows schematically theoperation of a typical limit switch.

Referring now to Fig. 1, I have shown my invention in one form asapplied to a preheat chamber 10 and a high-heat chamber 11. Each heatingchamber is provided with a plurality of rollers 12 arranged to form aroll table or roller hearth. In addition to the rollers provided in theheating chamber, a plurality of rollers are arranged at one end of thehigh-heat chamber 11 to form a run-out table 13. A crane 14 has aplurality of charge supporting carriers 15 adapted for movement betweenthe rollers of the run-out table so that the crane may be operated totransport a charge of work from the run-out table to a quenching bath16. From the quenching bath the crane 14 is arranged to place a chargeof work on the discharge rack 18. A charging mechanism 20 is arranged toplace charges of work within the preheat chamber 10.

Inasmuch as my invention is particularly suitable for automaticoperation, I have indicated at 22 the automatic controller whichcoordinates the operation of the several units of the furnace in amanner to insure continuous operation of the furnace. It will beunderstood, of course, that any suitable control system may be employedby those skilled in the art.

In explaining the operation of my invention with reference to Fig. 1, itwill be assumed that the line switch 23 has been closed and that acharge 24 has been placed in the preheat chamber 10 and a charge 25 hasbeen placed in the high-heat chamber 11. It will also be assumed thatthe charges 63 and 62 have been lowered on the charging mechanism 20.The controller 22 in conjunction with a limit switch LSK geared to theroll table will, therefore, cause the roller motor 30 to rotate first inone direction and then in the other direction through predeterminedlimits. Preferably the roller motor 30 rotates the rollers 12 through anangle greater than 180, for example 190, or through 360 first in onedirection and then in the other during the heating operation.Consequently, the charges 24 and 25 located respectively in the preheatchamber 10 and the high-heat chamber 11 are thereby reciprocated. Thesupporting area of each roller is constantly changed, by reason of theoscillation of the rollers, as well as the area of each bar of metalwhich is in contact with a roller. Consequently it will be seen thatthere are no unsupported lengths of metal during the heating operation.The limits of rotation of the rollers with reference to their diameterand their spacing are selected so that the rollers are moved intosupporting engagement with substantially the entire lengths of the bars.The sagging of the bars of metal between adjacent rollers is therebyeliminated. Furthermore, the cold spots between each roller and each barof metal are eliminated because the oscillation of the rollers resultsin the uniform heating of both the rollers and the bars. With referenceto the rollers, the requirement that the rollers shall be oscillatedthrough more than 180 is for the purpose of reversing the bendingstresses applied to the rollers so that permanent deflection of therollers is prevented.

The controller 22 after a predetermined time interval deenergizes themotor 30 and energizes the end door motor 32 in a direction to raise theend doors 33 and 34 of the high-heat chamber 11 and the end door 35 ofthe preheat chamber 10. As soon as the end doors are raised, a limitswitch LSD in conjunction with the controller 22 deenergizes the motor32 and energizes the roller motor 30 in a direction to rotate therollers in a counter-clockwise direction to cause the charges 24 and 25to progress through the furnace. As the charge 25 leaves the high-heatchamber 11 a bumper switch B2 is operated and serves to prevent thelowering of the end doors or the movement of the crane 14 until thecharge 25 has been completely transferred from the highheat chamber tothe run-out table. As soon as the charge 25 arrives on the run-out table13 a bumper switch B3 is operated to deenergize the roller motor 30. Thecharge 25 will then be in position on the run-out table to betransferred to the quenching bath 16, while the charge 24 will have beentransferred from the preheat chamber 10 to the high-heat chamber 11. Thebumper switch B3 in conjunction with the automatic controller 22 servesthree functions viz., the end door motor 32 is energized in a directionto lower the end doors, the hoisting motor 37 is energized in adirection to hoist the carriers 15 and the charge of work from therun-out table 13, and the motor 38 operating the side door 39 of thepreheat chamber 10 is energized in a direction to raise the side door.As soon as the side door is raised the limit switch LSBl stops the motorand in conjunction with the controller 22 energizes the motor 81 of thecharging mechanism 20 in a direction to raise the charging fork 43 sothat the charges 62 and 63 are raised above the stationary rack 60.

As soon as the end doors are lowered the limit switch LSD deenergizesthe end door motor 32.

As soon as the hoisting motor 37 raises the carriers 15 a predetermineddistance, this motor is deenergized by suitable limit switch mechanismin the controller 22 and the trolley motor 48 is thereupon energized ina direction to drive the crane 14 towards the quenching bath 16. As thecrane reaches the desired position over the quenching bath 16 thetrolley motor 48 is deenergized and the hoisting motor 37 is energizedin a direction to lower the carriers 15 and the charge of work into thequenching bath. The hoisting motor 37 is deenergized as the carriersreach a position corresponding to the broken line 49. Thereafter thehoisting motor 37 is energized first in one direction and then in theother direction, thereby causing the carriers to move the charge up anddown between the positions indicated by the broken lines 49 and 50. Themovement of the bars and carriers causes a flow of liquid over eachlength of the material besides creating a stirring action in thequenching liquid itself so that there is a uniform quenching of thematerial. After a predetermined time interval the hoisting motor 37 isenergized in a direction to hoist the charge in the quenching bath andthe trolley motor 48 is energized until it reaches the position over thedischarge rack 18 whereupon the hoisting motor 37 operates to lower thecarriers 15, leaving the charge supported on the dis charge rack 18. Thedischarge rack is designed with respect to the rim-out table 13 so thatthe hoisting motor 37 is deenergized to bring the carriers 15 to astandstill in the same horizontal plane they occupy at the run-outtable. Therefore, it is only necessary to energize the trolley motor 48,after a charge has been placed on the discharge rack 18, to drive thecarriers 15 directly to the run-out table in readiness for the nextcharge of work from the high-heat chamber. The motors 37 and 48 arecontrolled by suitable limit switch and timing mechanism which may beincorporated in the automatic controller 22.

Referring again to the charging mechanism, as soon as the motor 81 hasoperated the levers 71 and 74 to raise the charging fork 43, the limitswitch LSA, operated by the motor 81, in conjunction with the controller22 energizes the carriage motor 97 in a direction to move the chargingfork towards the preheat chamber 10. The charging fork is brought to astandstill within the preheat chamber by means of a limit switch LSCdriven by the motor 97. This limit switch also serves to energize themotor 81 in a direction to lower the charge of work between the rollers12. The charge 63 will then be supported by the rollers within thepreheat chamber. The motor 97 will then be energized by the limit switchLSA in a direction to drive the fork 43 from the preheat chamberwhereupon it is stopped in the position shown by the limit switch LSC.It will also be observed that the charge 62, after the completion of thecharging operation, has been transferred to the position on thestationary rack formely occupied by the charge 63. Additional chargescan be placed upon the stationary frame 60 by the shop crane or by anyother suitable means.

A complete cycle of operations has now been described and it will, ofcourse, be understood that the furnace may be operated continuously.

It will now be assumed that the furnace is empty and that the firstcharge of work is to be introduced into the preheat chamber. Thecharging mechanism functions to place a charge in the preheat chamber.After the first charge has been oscillated for the predetermined lengthof time the end doors raise and the charge is transferred to thehigh-heat chamber 11. The roller motor 30 is deenergized by means of abumper switch Bl operated by the arrival of the charge within thehigh-heat chamber. This bumper switch B1 is only operated by the firstcharge of work which enters the high-heat chamber. Thereafter the bumperswitch B3 at the end of the run-out table 13 controls the operation ofthe roller motor 30 in a manner which has already been described.

In the improved form of my invention embodied in Figs. 2 to 14,inclusive, the construction of the apparatus will first be describedwhile the operation of the furnace will be described in detail inconnection with the wiring diagram shown in Figs. 11 and 12.

charging mechanism Though any suitable charging mechanism may beemployed I prefer to utilize the mechanism described and broadly claimedin the copending application Serial No. 600,906, flled March 24,1932-Smith and Deery-and assigned to the same assignee as the presentinvention. This charging mechanism is simple in construction andparticularly lends itself to the handling of heavy charges of bars. Inthe present application the charging mechanism will be described bysaying that it consists of a stationary rack 60, Figs. 7 and 8, theupper rails 61 of which are arranged to support the charges of steelbars 62 and 63. These bars are held in position by means of the upwardlyextending lugs 64. The charging fork 43 is supported by an elevating andtransporting mechanism 66. As in the case of Fig. l, the charging forkconsists of a plurality of supports 67 supported in cantilever fashionby means of a plurality of downwardly directed extensions. Two of theseextensions 68 and 69 are shown in Figs. 7 and 8. The extension 68 ispivotally connected at 70 to one end of a lever 71. On the other end ofthis lever there are provided a plurality of gear teeth 72 arranged tomesh with a driving gear 73. Similarly, a lever 74 has gear teeth 75meshing with the gear 73 and is pivotally connected to the downwardextension 69 at 76. When the gear 73 is rotated in a counter-clockwisedirection the lever 71 rotating about its pivot point 77 exerts anupward thrust on the extension 68. Similarly, the lever 74 rotatingabout its pivot point 76 exerts an upward thrust on the extension 69.The result is a vertical raising of the charging fork 43. There areprovided six sets of similar elevating mechanism each being locatedbeneath one of the supports or forks 67.

Referring to Figs. 3 and 7, it will be observed that one of the drivinggears 73 is secured to a shaft 80 which extends the full width of thefork 43. The shaft is driven by a motor 81 which drives the gear 82secured to the shaft 80 through a suitable speed reducer 83. As the forkis moved from the position shown in Fig. 7 to the position shown in Fig.8, it will be seen that the steel bars 62 and 63 are transferred fromthe rails 61 to the fork 43. The lugs 85 provided on the charging forkmaintain the bars in grouped relation so that they cannot shift from theposition shown. The limit switch LSA geared at 86 to the shaft 80serves, as a part of its function, to deenergize the motor 81 as thefork is raised to its upper or charging position. The translationalmovement of the fork is made possible by a transporting carriage 90. Thefork 43 and levers 71 and 74 and the motor 81 are supported on thecarriage 90. The carriage wheels, which are shown, ride upon a track 93.Supported from the carriage frame is a rack gear 94 arranged to meshwith a driving gear 95. The latter gear is driven by a motor 97 which ismechanically connected through a suitable speed reducer 98 to the shaft99 to which the gear is secured. A limit switch LSC geared to the shaft99 serves as a part of its function to control the energization of thecarriage motor 97.

The preheat chamber It will be observed that the preheat chamber 10,Figs. 3 and 4, is provided with a plurality of rollers 12 forming aroller hearth within the preheat chamber. This roller hearth serves as asupport for the charges of work as well as for the transfer of the workthrough the furnace. Within the preheat chamber there are provided theheating resistors 100 and 101, Fig. 7.

As shown, the side door 39 can be raised and lowered by the motor 38geared to the hoisting drums 103 upon which the door cables 104 arewound. The counterweights 105 are secured at one end oi the respectivedoor cables. The moby means of a super-structure 106 formed of steelbeainsorthelike. Apair oftracktypelimit switches 1331 and 15132 (seeFig. 4) serve as a part of their function to deenergize the side doormotor 38 as the door is driven to one or the other of its positions. Therollers of the roll table are arranged to be driven by the motor 30which, as will be observed (Fig. 3), isgeared toa shaft 108 which servesto drive each roller of the roll table through suitable connectinggearing.

The end door motor 32 is molmted upon a superstructure 109 and serves toraise and to lower the end door 35 on-the preheat chamber and the enddoors 33 and 34 on the high-heat chamber. A limit switch ISD, shown inFig. 9, serves as a part of its function to deenergize the end doormotor 32 as the doors reach one or the other of their limits.

The high-heat chamber The high-heat chamber 11, Figs. 4, 5 and 9, issimilar in construction to the preheat chamber but additional heatingresistors are provided inasmuch as the temperature of this unit of thefurnace is to be considerably higher than the temperature of the preheatchamber. The materials for the construction of the furnace and of theroller hearth will of course be selected with reference to the hightemperature at which this unit of the furnace is to operate.

The run-out table The run-out table 13, Figs. 5, 6 and 10, consists ofan extension of the roll table. However, the rollers are spacedsufllciently apart to permit the carriers 15 provided on the crane 14 totravel between them. The bumper switches B1, B2 and B3 perform the samefunctions as described in connection with Fig. 1.

The crane The carriers 15 are supported from one end 112 by the steelsupports 113 and 114. These supports are secured to a framework 116which has mounted upon it a plurality of pulleys, two of which 117 and118 are shown in Fig. 10. About these pulleys are threaded thesupporting cables 119 and 120 which are wound upon the hoisting drum121. A truck 122 mounted on a track 123 supports the hoisting drum 121as well as the hoisting motor 3'1 and the trolley motor 48. The track123 extends over the quenching tank 16 and the discharge rack. A pair ofgeared limit switches LSH and [ST are respectively provided forcontrolling the energization of the hoisting motor 3! and the trolleymotor 48. There is also provided a track-type limit switch LSH2 operatedby the crane to deenergize the hoisting motor 3'7 whenever the carriers15 are hoisted to a podtion a predetermined distance above the run-out.table.

The automatic control system It is believed that a clear understandingof the arrangement and operation of the various parts of a suitableelectrical system will be best understood from a complete description ofthe operation of the system as a whole, and therefore the constructionand arrangement of certain typical devices only will be first describedin detail.

The limit switches ISA. 18K. 15D, 15C, 1ST and LSH are constructed asshown in Fig. 14. Each pair of contacts 110 are arranged to be bridgedby a conducting member 111, pivotally tor 38 and the hoisting drum 103are supported mounted at 112 on a support 113. A spring 114 normallybiases the conducting member 111 away from the contacts 110. A lug orcam 115 is secured to a disk 116 mounted on a shaft 117, and serves tocooperate with a roller 118 carried by the contact arm 119 so as tooperate the conducting segment 111 to close the contacts 110. As thecontact arm 119 is rotated about its pivot 112, its lower end 120 isengaged by a latching member 121 holding it in its closed position. Thelatching member 121 is biased against the lower end 120 of the switchmember 119 by a spring 122. A second lug or cam 123 is arranged toengage a roller 124 so that the latching member 121 may be rotated aboutits pivot point releasing the switch member 119 so that the spring 114may operate the switch member to open the contacts 110. It willtherefore be observed that the limit switch contacts require positiveoperations for both the opening and the closing of the contacts.

A plurality of sequence relays L1, L2, L3, L4, L5, L6 and L'Iarearranged so that when an energizing circuit is completed for one of thesequence relays, it will be operated and latched into pofition. In otherwords, it will require a second circuit to be completed to unlatch thesequence relay so that it may be operated into its unlatched position.By means of this type of relay the sequence of operations of the cyclewill not be disturbed even though there is a power failure. This will beseen by observing that the relays and contactors normally held closed byreason of energizating circuits completed thru the contacts of thesequence relays, upon power failure will be operated to their openpositions. As soon as there is a resumption of power, however, therelays and contactors will be closed, inasmuch as the sequence relaysmaintain the energizing circuits.

The timing relays TF, TR, 226, 227, 228, 229 and TR2 are similarlyconstructed. For example, timing relay TF (Fig. 11) is provided with ashort circuited winding 230. After the operating coil of the relay TFhas been energized to cause its contacts to be opened and thereafter itsenergizing circuit is broken, it will be understood that the shortcircuited coil 230 serves to decrease the rate of decay of the magneticflux thereby maintaining the contacts of the time relay open for apredetermined time interval. A timing relay 'I'Rl is provided with asuitable device 231 arranged to delay the closing of the contacts ofthis relay.

A master timer 232 is arranged to control the length of time a chargeshall remain in one of the heating chambers. This timer has a pair ofcontacts 233 which are normally open. when the timer is in operationalternating current is applied to its motor 234 and to the operatingcoil 235. The armature 236 of this motor is thereby rotated and byreason of the magnetic attraction of the coil 235 exerted on a magneticmember 237, the worm gear 238 is rotated into engagement with the gear239. Just enough movement is permitted by a stop member 240 so that theworm gear 238 may be moved about the pivot 241 into meshing engagementwith the gear 239. However, the stop member 240 does not permit theclosing of the contacts 233. As soon, however, as the outwardlyextending projection or tripping member 242 carried by the gear 239strikes the latching member 243, the coil 235 closes the contacts 233.By varying the position of the tripping member 242 with respect to thelatching member 243, it will be observed that the time required for theclosing of the contacts 233 may be varied. A similar timer 738 isarranged to control the time required for the quenching operations.

It is now believed that a comprehensive understanding of the system,including the construction and arrangement of various devices, will befacilitated by a description of the operation of the system as a whole.While any suitable system may be used I have shown the system describedand claimed in a copending application of A. F. Betke, Serial No.614,234, flled May 28, 1932, and assigned to the same assignee as thisinvention.

Referring to Figs. 11, 12 and 13, a pair of line switches 250 and 251are shown closed, so that the supply lines 252 and 253 are connected toa suitable source of direct current supply (not shown). The supply line252 is connected to the source of supply by means of an undervoltagerelay 254 which is energized through a circuit which may be tracedthrough the line switch 250, push button stations 255 and 256, conductor257, operating coil of the relay 254, and by conductors 258 and 259 tothe other supply line 253. It will be observed that the supply line 252serves as the origin of all of the control circuits and therefore ifthere should be a voltage failure of the supply source, all of thecontrol circuits will be deenergized by reason of the opening of therelay 254. The stop push buttons 255 and 256 may be multipliedindefinitely, that is to say, fifteen or twenty of these push buttonsmay be distributed at various points about the furnace so that in caseof the occurrence of an abnormal condition, the operator may deenergizeall of the control circuits by simply pressing a stop push button, whichit will be observed, interrupts the circuit to the relay 254.

It will be observed that the supply line 253 is connected to the sourceof supply by a normally closed switch 253a. While only one of theseswitches is shown in Fig. 11 of the drawings it is to be understood thateach door may be provided with a similar switch. Should the work comeinto engagement with an end door thereby causing the end door to beswung outwardly from its supporting cables, all of the control circuitswill be deenergized by the opening of the switch 253a.

To clarify the description, the line switches 250 and 251 are shownclosed. Consequently a number of contactors and relays are shown intheir energized positions before the start push button 261 has beendepressed to initiate the automatic operation of the furnace. Forexample, an energizing circuit for the timing relay TR may be tracedfrom the supply line 252, by conductor 262', operating coil of thetiming relay TR, contacts 263 of the limit switch LSK, and by conductors264, 265 and 259 to the other supply line 253. An energizing circuit forthe first accelerating relay 226 of the roll motor 30 may be traced fromsupply line 252, by conductor 266, normally closed contacts 267 of thesequence relay L3, conductor 266a, contact 268 of the forward directionswitch 269 provided for the roll motor 30, conductor 270, operating coilof the relay 226, and by conductors 271, 265 and 259 to the other supplyline 253. A similar accelerating relay 227 provided for the carriagemotor 97 is energized through a circuit which may be traced from thesupply line 252 by conductors 274, 276, 277, contacts 279 provided onthe direction switch 280 for the out-motion of the carriage motor 97,interlock contacts 281 provided on the direction switch 282 for thein-motion of the carriage, operating coil of relay 227, and byconductors 283 and 285 to the other supply line 253. A fieldaccelerating contactor 287 of the hoist motor is closed by reason of anenergizing circuit which may be traced from supply line 252, byconductors 274, 276. 288, contacts 289 of hoisting relay 290, conductor291, contacts 292 of the lowering relay 293, conductor 294, operatingcoil 295 of the contactor 287 and by conductor 296 to the other supplyline 253. An accelerating contactor 298 provided for the crane hoistingmotor 37 is energized by reason of a circuit which may be traced fromthe supply line 252, by conductor 299, contacts 300 provided on therelay 301, conductor 302, interlock contacts 303 provided on thehoisting relay 290, interlock contacts 304 provided on a loweringdirection switch 305, conductor 306, operating coil 307 of the contactor298, and by conductors 308 and 259 to the other supply line 253. Anenergizing circuit for the accelerating contactor 309 is derived bymeans of a conductor 310 from the energizing circuit for the contactor298 and is completed through the contacts 311 operated with thecontactor 298, operating coil of contactor 309 and by conductor 259 tothe other supply line 253. The completion of the energizing circuit ofthe field accelerating contactor 312 of the hoist motor depends on thecontacts 313 operated with the contactor 309. This circuit may be tracedfrom supply line 252 by conductors 274, 276, 314, 315, contacts 313 ofthe contactor 309, contacts of the relay 229, operating coil 316 of thecontactor 312 and by conductor 317 to the other supply line 253.

An undervoltage relay 321 is provided to protect the furnace and thework from overheating in case of power failure of the direct currentsource of supply. Its energizing circuit may be traced from the supplyline 252 by conductor 322, operating coil of the relay 321, and byconductors 323 and 285 to the other supply line 253. An energizingcircuit for a contactor 327, arranged to connect the heating resistorsdesignated at 328 and located in the preheat and the high-heat chambersto a suitable three phase source of supply as is indicated by the supplylines 329, 330 and 331, may be traced from the supply line 329, contacts332 of the undervoltage relay 321, conductor 333, operating coil of thecontactor 327, and by conductor 334 to the other supply line 330. Acontrol panel 335 is provided with a number of control switches (notshown) which serve to complete the power circuits from the three phasesource of supply to the various heating resistors employed for theheating of the furnace.

The contacts 337 provided on the undervoltage relay 321 serve tocomplete an energizing circuit for the master timer 232.

The circuit for the timer motor 234 may be traced from the alternatingcurrent supply line 329, contacts 340 of the timer, conductor 341, motorwinding of the timer, conductor 343, contacts 344 of the end door limitswitch LSD, conductor 345, contacts 337 of the undervoltage relay 321,and by conductor 346 to the other supply line 330. The circuit to theoperating coil 235 of the timer may be traced from the supply line 329by conductor 347, coil 235, conductors 348 and 343, contacts 344 of theend door limit switch LSD, conductor 345, contacts 337 of undervoltagerelay 321 and by conductor 346 to the other supply line 330. It willtherefore be observed that as soon as voltage is applied to the supplylines 252 and 253 and to the alternating current supply lines 329, 330and 331, the master timer 232 begins timing in the manner that hasalready been explained.

For the sake of clarity of description it will be assumed that theinitial heating of the furnace has been completed and that the preheatchamber 10 and the high heat chamber 11 have been brought up to theirnormal operating temperatures.

To initiate the automatic operation of the furname under the conditionsassumed and with the various parts in the positions shown in Figs. 11and 12, a normally open start button 261 is momentarily depressed toestablish an energizing circuit for a normally open relay 351. Thiscircuit may be traced from supply line 252, by conductor 352, pushbutton 261, operating coil of the relay 351, and by conductors 353 and259 to the other supply line 253. The relay 351 is thereupon closed tocomplete energizing circuits through its contacts 355, 356 and 357.

The bumper switch B1, which it will be remembered is located in the highheat chamber 11, is rendered effective by reason of the completion ofits energizing circuit by the contacts 35'! of the relay 351. Thiscircuit may be traced from the supply line 252 by conductor 359,contacts 357 of the relay 351, conductor 360, operating coil 361 of thebumper switch B1, and by conductor 285 to the other supply line 253. Thecontacts of the bumper switch B1 are thereupon opened and the pivotedmember 88 (see Fig. 5) is moved into the path of the work. This bumperswitch serves to deenergize the roll table motor 30 as the first chargeof work arrives in the high heat chamber from the preheat chamber.Thereafter this bumper switch is not effective, inasmuch as the rollmotor for subsequent operation is deenergized by the opening of thecontacts 362 of the relay 301, which relay is operated due to theclosing of the contacts of the bumper switch B3 located on the outer endof the run-out table 13 (see Fig. 5).

Incident to the closing of the contacts 356 of the relay 351 thesequence relay L5 is operated to its latched-in position by reason of anenergizing circuit which may be traced from the supply line 252 byconductor 364, contacts 356 of the relay 351, conductor 365, operatingcoil 366 of the uence relay L5, and by conductors 367 and 259 to theother supply line 253. The opening of the contacts 3'10 of this relayremoves a shunt circuit around the contacts 3'11 of the relay 3'12, andinasmuch as this relay operates to open its contacts 3'11 following theoperation of the bumper switch B1, it will be seen that the energizingcircuit for the forward direction switch 269 of the roll motor 30 maythereby be interrupted. The closing of the contacts 3'13 of the sequencerelay L5 causes the closing of the relay 3'14 by reason of thecompletion of its energizing circuit. This circuit may be traced fromthe supply line 252 by conductor 3'15, contacts 3'13 of the sequencerelay L5, conductor 3'16, operating coil of the relay 3'14, and byconductors 3'17 and 285 to the other supply line 253. The contacts 3'18of the relay 3'14 serve partially to complete an energizing circuit forthe direction switch 385 of the cams, while the relay contacts 380 servepartially to complete an energizing circuit for the lower directionswitch 381 of the end door motor 32.

The closing of the contacts 355 of the relay 351 completes an energizingcircuit for the sequence relay L1, which circuit may be traced fromsupply line 252, by conductor 364. contacts 355, 0p-

crating coil of the sequence relay L1, and by conductors 383 and 259 tothe other supply line 253. The sequence relay L1 is thereupon operatedto its latched-in position with its contacts 384 closed. The closing ofthese contacts completes an energizing circuit for the up-directionswitch 385 of the lever motor 81. This circuit may be traced from thesupply line 252, by contacts 386 of the bumper switch B2, contacts 387of the side door limit switch LSB2, contacts 388 of the lever limitswitch LSA, contacts 384 of the relay L1. operating coil 389 of thedirection switch 385, interlock contacts 391 of the lower directionswitch 382 of the lever motor, and by conductors 393 and 259 to theother supply line 253.

The closing of the up-direction switch 385 serves to connect thearmature of the motor 81 by conductors 395 and 396 to a suitable sourceof direct current supply as is designated by the positive and negativesymbols. A separately excited fleld winding 397 for this motor issimilarly energized as indicated from a suitable source of directcurrent supply. The lever motor 81 is thereupon caused to rotate in adirection to raise the charging fork 43 as previously described. It willbe understood that accelerating contactors may be employed to acceleratethe motor 81 though these have been omitted for the purpose ofsimplifying the drawings.

When the up direction switch 385 closed, the contacts 399 operated withthis switch were closed to establish an energizing circuit for theoperating coil 400 of the sequence relay L6. This circuit may be tracedfrom the supply line 252 by conductor 401, contacts 399 of the directionswitch 385, conductor 403, operating coil 400 of the sequence relay L6,and by conductors 404 and 259 to the other supply line 253. The sequencerelay L6 is thereupon operated and latched into position with itscontacts 405 closed complete in part and energizing circuit for thein-direction switch 282 of the carriage motor 9'1. At the same time thecontacts 406 of the relay L6 are opened to prevent the completion of anenergizing circuit for the out-direction switch 280. The interlocking ofcircuits in this manner maintains the carriage within the furnace untilthe load transferring operations have been completed.

As soon as the lever motor 81 has raised the charging fork 43 to itsupper position, the limit switch LSA is operated to open its contacts388,

407 and 408, while its contacts 409 and 410 are closed. The opening ofits contacts 388 deenergizes the up-direction switch 385, which switchis operated to deenergize the motor 81.

The closing of the contacts 409 of the limit switch LSA serves tocomplete an energizing circuit for the raise direction switch 412 of theside door motor 38. This circuit may be traced from the supply line 252by conductor 413, contacts 414 provided on the side door limit switchLSBl, contacts 409 of limit switch LSA, conductor 415, operating coil416 of direction switch 412, interlock contacts 41'! of the loweringdirection switch 3'19 and by conductors 418, 265 and 259 to the othersupply line 253. The direction switch 412 thereupon closes to connectthe armature of the motor 38 by conductors 419 and 420 to a suitablesource oi direct current supply designated by the positive and negativesymbols. The motor 38 is provided with a separately excited fieldwinding 421 which is energized from a suitable source of direct currentsupply as indicated. The motor 38 is therefore caused to rotate in adirection to raise the side door.

As soon as the side door reaches its upper position the track type limitswitch LSBl is operated to open its contacts 414 and to close itscontacts 422. The opening of the former contacts deenergizes thedirection switch 412 which in turn deenergizes the motor 38. Thecontacts 422 of the limit switch LSBI serve to complete the energizingcircuit for the in-direction switch 282 of the carriage motor 97. Thiscircuit may be traced from the supply line 252, by conductor 423,contacts 422 of LSBl, conductor 424, contacts 405 of the sequence relayL6, conductor 425, contacts 426 of the carriage limit switch LSC,conductor 427, operating coil of the direction switch 282, interlockcontacts 428 of the out-direction switch 280, and by conductor 285 tothe other supply line 253. The direction switch 282 is thereupon closedto energize the carriage motor 97 to cause it to be rotated in adirection to move the carriage and the charging fork 43 towards thepreheat chamber 10. A separately excited field winding 430 is providedon the carriage motor 97 to provide excitation therefor.

It will be remembered that the energizing circuit for the acceleratingrelay 227 of the carriage motor was traced through the contacts 281 onthe in-direction switch 282. Therefore, as soon as the direction switchwas operated this circuit was broken by the opening of the contacts 281.After a predetermined time interval introduced by reason of the shortcircuited coil 227a its contacts are closed to establish an energizingcircuit for the accelerating contactor 431. This circuit may be tracedfrom the supply line 252 by conductors 274, 276, 277, contacts of theaccelerating relay 227, operating coil of the accelerating contactor 431and by conductors 433 and 285 to the other supply line 253. Theaccelerating contactor 431 is therefore operated to its closed positionto short circuit the resistance 434 connected in series with thearmature of the motor 97.

While I have only shown a single accelerating contactor for the carriagemotor 97, it will be understood that several accelerating contactors maybe used to provide smooth acceleration of the carriage motor. However,as I have indicated in connection with the lever motor 81, theaccelerating contactors have been omitted for the purpose of simplifyingthe drawings wherever the function of these contactors are well knownand well understood by those skilled in the art.

As the carriage nears its limit of movement with the charging fork 43and the load 63 within the preheat chamber, the limit switch LSC isoperated to open its contacts 426 and 436 and to close its contacts 437and 438. It will be observed that the operating coil of the directionswitch 282 is deenergized due to the opening of the contacts 426 of thelimit switch LSC. As this direction switch is operated to its openposition its contacts 439 are closed to establish a dynamic brakingcircuit for the carriage motor 97 through a resistance 440. This circuitmay be traced from one side of armature of the carriage motor 97 bycontacts 439 operated with the direction switch 282 dynamic brakingresistance 440, contacts 441 operated with the direction switch 280, andby conductor 442 to the other side of the armature of the motor 97.

The positions of the carriage 90 and the charging fork 43 as they cometo a standstill are shown in Fig. 8.

The closing of the contacts 437 of the limit switch LSC serves toestablish an energizing circuit for the down-direction switch 382 of thelever motor 81. This circuit may be traced from the supply line 252, byconductor 446, contacts 410 of the limit switch LSA (which contacts itwill be remembered were closed when the charging fork 43 was raised bythe lever motor 81) interlock contacts 448 of the direction switch 385,operating coil of the lower-direction switch 382, conductor 450,contacts 437 of the limit switch LSC, and by conductors 451 and 259 tothe other supply line 253. The motor 81 is thereupon caused to berotated in a direction to lower the charging fork 43 thereby depositingthe load 63 on the roll table and the load 62 on the stationary rack 60.

Incident to the closing of the lower direction energizing circuit forthe trip coil 452 of the sequence relay L1 is completed by the closingof the contacts 453 operated by the downdirection switch 382. Thiscircuit may be traced from supply line 252 by conductor 454, trip coil452 of the sequence relay L1, contacts 453 of the down-direction switch382, and by conductors 455 and 259 to the other supply line 253.Similarly, the contacts 456 operated with this direction switch wereclosed to complete an energizing circuit for the trip coil 457 of thesequence relay L6. This circuit may be traced from the supply line 252,conductor 458, contacts 456 of direction switch 382, conductor 459, tripcoil 457 and by conductors 404 and 259 to the other supply line 253. Itwill be remembered that the sequence relay L6 was operated to itslatched-in position so that the in-direction switch 282 of the carriagemotor could be energized, and so that the energizing circuit of theout-direction switch 280 could not be completed. Therefore, it will beseen that as soon as the trip coil 457 releases the sequence relay L6this relay is operated to its unlatched position to close its contacts406, thereby partially completing an energizing circuit for theout-direction switch 280 of the carriage motor 97.

As the charging fork 43 is lowered, the contacts 409 and 410 of thelever limit switch LSA are operated to their open positions, while thecontacts 388, 407 and 408 of the lever limit switch LSA are operated totheir closed positions. The opening of the contacts 410 serves todeenergize the down-direction switch 382, which switch is operated toits open position to deenergize the lever motor 81. At the same time thecontacts 408 of the limit switch LSA complete the energizing circuit forthe out-direction switch 280 of the carriage motor 97. This circuit maybe traced from the supply line 252 by conductor 461, contacts 408 of thelimit switch LSA, conductor 462, contacts 406 of the sequence relay L6,conductor 464, contacts 438 of the limit switch LSC, conductor 466,operating coil of the out-direction switch 280, interlock contacts 468of the in-direction switch 282, and by conductor 285 to the other supplyline 253. The outdirection switch 280 is thereupon closed to energizethe motor 97 in a direction to drive the carriage 90 and the chargingfork 43 from the preheat chamber. As before, the accelerating relay 227closes after a predetermined interval of time to energize theaccelerating contactor 431. In this case the circuit to the acceleratingrelay 227 is broken by reason of the opening of the contacts 279,operated with the out-direction switch 280.

As the carriage is driven to its outer position as shown in Fig. 7, thecontacts 437 and 438 of the carriage limit switch LSC are operated totheir open positions while the contacts 426 and 436 of this switch areoperated to their closed positions. The out-direction switch 280 isdeenergized and operated to its open position as a result of the openingof the contacts 438 of the limit switch LSC. As this switch is operatedto its open position the contacts 441 operated with it are closed toestablish a dynamic braking circuit for the carriage motor 9'7 so thatthe motor is quickly braked to a standstill with the carriage and thecharging fork in their original positions.

Incident to the closing of the contacts 436 of the carriage limit switchLSC the lower direction switch 3'79 of the side door motor 38 is closedby reason of an energizing circuit which may be traced from the supplyline 252 by conductor 4'72, contacts 473 of the limit switch LSB2,contacts 407 of the limit switch LSA, conductor 4'75, interlock contacts4'76 of the direction switch 412, operating coil of the direction switch3'79, conductor 477, contacts 436 of the limit switch LSC, and byconductors 478, 451 and 259 to the other supply line 253. As a result ofthe closing of the direction switch 3'79, the motor 38 is energized in adirection to lower the side door 39.

Inasmuch as the carriage and the charging fork 43 have been driven fromthe preheat chamber and the door is being lowered, the roll motor maynow be energized in a manner to cause the oscillation of the charge inthe preheat chamber 10. The sequence relay L3 controlling theenergization of the roll motor 30 is therefore closed as soon as theside door motor direction switch 3'79 is operated to its closed positionby reason of an energizing circuit completed by the closing of thecontacts 480 operated with this direction switch. This circuit may betraced from the supply line 252 by conductors 481, operating coil 482 ofthe sequence relay L3, conductor 484, contacts 480 of the directionswitch 379 and by conductors 485, 265 and 259 to the other supply line253. The sequence relay L3 is thereupon operated to its latched-inposition with its contacts 487 closed and its contacts 267 open.

As soon as the side door 39 reaches its lower limit, the contacts 4'73of the side door limit switch LSB2 are operated to their open positionto deenergize the direction switch 3'79. At the same time the contacts387 of this limit switch are closed.

As soon as the sequence relay L3 is latched into position the armatureof the roll motor 30 is shunted by a resistance 490 while the energizingcircuit to the accelerating contactors 495 and 496 are interrupted sothat the series resistances 497, 498 and 500 remain effective.Consequently, the motor 30 may only rotate at a very low speed to changeprogressively the load supporting area of each roller. The opening ofthe contacts 267 of the sequence relay L3 accomplishes the interruptionof the energizing circuits to the accelerating contaetors. The shuntconnection of the armature of motor 30 with the resistance 490 isaccomplished by reason of the completion of an energizing circuit forthe contactor 501. This circuit may be traced from the supply line 252by conductor 502, contacts 487 of the sequence relay L3, conductor 503,operating coil of the contactor 501 and by conductors 504. 265 and 259to the other supply line 253. As soon as the contactor 501 is closed, anenergizing circuit is completed for the clutch operating coil 515 due tothe closing of the contacts 514 operated with the contactor 501. Thiscircuit may be traced from the supply line 252 by conductor 516, clutchoperating coil 515, conductor 517, contacts 514 of the contactor 501,and by conductors 518, 265 and 259 to the other supply line 253. Thesolenoid 515 thereupon operates the clutch member 519 into engagementwith a cooperating clutch member 520 thereby establishing a mechanicalconnection between the driving motor 30 and the limit switch LSK. Theforward direction switch 269 of the roll motor 30 is operated to itsclosed position as a result of the closing of the contacts 487 of thesequence relay L3. This energizing circuit may be traced from the supplyline 252 by conductor 502, contacts 487 of the sequence relay L3,conductor 522, contacts of the time closing relay TF, conductor 524,contacts 525 of the push button station 526, conductor 527, contacts 528of the limit switch LSK, contacts 362 of the relay 301, contacts 3'71 ofthe relay 3'72, operating coil 530 of the forward direction switch 269,interlock contacts 531 of the reverse direction switch 532 of the rollmotor 30, and by conductors 533, 265 and 259 to the other supply line253. The direction switch 269 thereupon closes to energize the motor 30so that it drives the rollers in a forward direction. A separatelyexcited field winding 534 provides excitation for this motor. It will beobserved that this field winding 534 is connected in series with aresistance 535. A relay 536 has its operating coil connected across theseries resistances 497, 498, and 500. As soon as current flows to thearmature of the motor 30 the resulting potential difierence existingacross the series resistances 497, 498 and 500 is suflicient to causethe operating coil of the relay 536 to dose its contacts, thereby shortcircuiting the field resistance 535. The result is an increase in fieldcurrent and a consequent reduction in the speed of rotation of the motor30.

As soon as the motor 30 has driven the rollers through approximately 190degrees, the contacts 528 of the limit switch LSK are operated to theiropen position, thereby deenergizing the direction switch 269. At thesame time, the contacts 263 of the limit switch 18K are operated totheir open position, while the contacts 538 and 539 are operated totheir closed positions.

The closing of the contacts 539 of the limit switch LSK serves partiallyto complete an energizing circuit for the reverse direction switch 532of the roll motor 30.

It will be remembered that the energizing circuit for the timing relayTR was traced through the contacts 263 of the limit switch LSK.Therefore, as soon as these contacts were operated to their openposition, they served to interrupt this 1.2.30 energizing circuit. Aftera predetermined interval of time the contacts of the time closing relayTR. are closed to complete the energizing circuit for the reversedirection switch 532 of the roll motor. This circuit may be traced fromthe su ply line 252 by conductor 502, contacts 487 of the sequence relayL3, conductor 522, contacts of the timing relay TR, contacts 539 of thelimit switch LSK, conductor 540, interlock contacts 542 of the directionswitch 269, operating coil 543 of the direction switch 532, and byconductors 544,

265 and 259 to the other supply line 253.

The direction switch 532 is thereby closed to energize the roll motor 30for reverse direction of rotation. The field relay 536 again closes toshort circuit the field resistance 535 so that the speed of the motor isvery low.

The closing of the contacts 538 of the limit switch LSK serves tocomplete an energizing circuit for the time closing relay TF. Thiscircuit 1,979,108 supply line 252 by con-- predetermined time interval,

The direction switch 269 is thereby energized by means of the circuittraced above and the motor 30 again rotates in the forward direction atvery low speed. The closing of the contacts 263 of the limit switch LSKserves to again complete the energizing circuit for the timing relay TR,which is immediately operated to open its contacts so that it is inreadiness for the next operation of the roll motor.

The described cycle of operations serves constantly to shift the workback and forth in the preheat chamber. The result is the uniform heatingof the material as well as the prevention of the deformation of therollers or the work due to uneven heating. It is to be understood thatthe rollers may be rotated through 180 or more. If the rollers wererotated through 360 first in one direction and then in the otherdirection, it would not be necessary to introduce the time intervalbetween reversals; that is to say for a 360 cycle the load supported bythe rollers is equally distributed over the entire surface of therollers. I have found, however, that by rotating the rollers throughmore than 180 but less than 360 and by introducing a time intervalbetween reversals roller bending and/or deformation may be substantiallyif not entirely eliminated. An economy in furnace size is also attainedby decreasing the roller travel to less than 360. i

The contacts 550 and 551 of the limit switch LSK are arranged to beoperated to their closed positions as soon as roll motor 30 has rotatedthrough a given angle in a forward direction. Thereafter they areimmediately operated to their open positions so that the contacts 550and 551 remain closed only for a short interval of time as the motor 30is rotated in a forward direction. These limit switch contacts have fortheir function the partial completion of energizing circuits forproducing at the proper time the high speed operation of the motor 30.In other words the transfer of work from one heating chamber to anothermay only be initiated with the rollers occupying a predeterminedposition.

After the load 63 of steel bars has been oscillated in the preheatchamber for a period of t me as determined by the setting of the mastertimer 232, the master timer times out thereby closing its contacts 233.It will be assumed that these contacts are closed just as the rollerposition determining contacts 550 and 551 of the limit switch LSK areclosed. The raise-direction 'switch 552 of the end doors is immediatelyclosed B by reason of the completion of an energizing circuit which maybe traced from the supply line 252, by conductor 554, contacts 551 ofthe limit switch LSK, conductor 555, contacts 233 of the master timer232, conductors 556 and 837, contacts 557 of the end door limit switchLSD, conductor 558, operating coil 559 of the raise direction switch552, interlock contacts 560 of the lower direction switch 381, and byconductors 323 and 285 to the other supply line 253. The motor 32 isimmediately energized in a direction to raise The closing of thecontacts 562 operated with the direction switch 552 serves to completean energizing circuit for the trip coil 565 of the sequence relay L3.This circuit may be traced from the supply line 252 by conductor 566,contacts 550 of the limit switch LSK, trip coil 565 of the sequencerelay L3, conductors 567 and 568, contacts 562 of direction switch 552and by conductors 569, 264, 265 and 259 to the other supply line 253.The sequence relay L3 is thereupon operated to its unlatched positionwith its contacts 267 closed and its contacts 487 open. The opening ofthe contacts 487 interrupts the energizing circuit of the contactor 501which is immediately operated to its open position. The opening of thecontacts 514 operated with the contactor 501 serves to deenergize theclutch operating coil 515 of the limit switch LSK so that the clutchmember 519 immediately disengages itself from the clutch member 520. Theopening of the contacts 487 of the sequence relay L3 it will beremembered also serves to deenergize the forward direction switch 269 ofthe roll motor which switch immediately operates to its open position.As the direction switch 269 opens, the contacts 268 operated with thisswitch are closed to complete an energizing circuit for the accelermaybetraced from the supply line 252 by conductor 266, contacts 267 of thesequence relay L3, contacts 268 of the direction switch 269, conductor270, operating coil of the accelerating relay 226, and by conductors271, 265 and 259 to the other supply line 253. The accelerating relay isthereupon operated to open its contacts so as to be in readiness for thehigh speed operation of the motor.

As soon as the end doors have been raised to their upper positions, theend door limit switch LSD operates to close its contacts 571, 573, 574and to open its contacts 557, 575 and 344. The contacts 577 and 578 ofthis limit switch 'are arranged to be closed only as the end doors arebeing lowered. The opening of the contacts 557 interrupts the energizingcircuit to the direction switch 552 which is immediately operated to itsopen position to deenergize the end door motor 32.

The closing of the contacts 573 of the end door limit switch LSD servesto complete an energizing circuit for the forward direction switch 269of the roll motor 30. This circuit may be traced from the supply line252 by conductor 554, contacts 551 of the limit switch LSK, contacts 573of the limit switch LSD, conductor 580, contacts 362 of the relay 301,contacts 371 of the relay 372, conductor 582, operating coil 530 of thedirection switch 269, interlock contacts 531 of the reverse directionswitch 532, and by conductors 533, 265 and 259 observed that the rollfor rotation in the forward direction. The accelerating relays 581 and585 are operated to their open positions by reason of the IR drop acrossthe resistance 497. The opening of the contacts 268 operated with thedirection switch 269 interrupted the energizing circuit traced above forthe accelerating relay 226. This relay therefore time closes to completean energizing circuit for the first accelerating contactor 495. Thiscircuit may be traced from the supply line 252 by conductor 266,contacts 267 of the sequence relay L3, conductor 266a, and 582, contactsof the accelerating relay 226, conductor 584, operating coil of thecontactor 495, and by conductors 271, 265 and 259 to the other supplyline 253. The closing of the contactor 495, it will be observed, shortcircuits the series resistance 497, and also short circuits theoperating coil of the second accelerating relay 581, which coil, it willbe observed, is connected directly across the resistance 497. The resultis that the motor 30 is accelerated a predetermined amount; after a.predetermined interval of time, the relay 581 time closes to energizethe second accelerating contactor 496. This circuit may be traced fromthe supply line 252 by conductor 266, contacts 267 of the sequence relayL3, conductor 266a and 582, contacts of the accelerating relay 226,conductor 584, contacts of the accelerating relay 581, operating coil ofthe accelerating contactor 496, and by conductors 265 and 259 to theother supply line 253. This contactor thereupon closes to short circuitthe second accelerating resistance 498 from the armature circuit of themotor'30. Inasmuch as the accelerating relay 585 has its operating coilconnected across the resistances 497 and 498,'the closing of the secondaccelerating contactor short circuits the operating coil of theaccelerating relay 585. After a predetermined interval of time thisrelay operates to close its contacts thereby completing an energizingcircuit for the third accelerating contactor 588. This circuit may betraced from the supply line 252 by conductor 266, contacts 267 of thesequence relay L3, conductor 266a and 582, contacts of the acceleratingrelay 226, conductor 584, contacts of the accelerating relay 585,operating coil of the contactor 588, and

- by conductors 265 and 259 to the other supply line 253. The closing ofthe contactor 588 serves to short circuit the resistances 497, 498 and500 so that the motor 30 is accelerated to substantially full speed. Itwill be remembered that the field accelerating relay 536 is connectedacross the series resistances 497, 498 and 500, so that as soon as thecontactor 588 removes these resistances from the armature circuit of themotor 30, the operating coil of the field relay 536 is short circuited.The field relay thereupon opens its contacts to reinsert the resistances535 in the circuit of the field winding of the motor 30, causing theacceleration of the motor to its full speed.

By thus providing for the rapid acceleration of the motor 30, the load63 of steel bars is rapidly transferred from the preheat chamber 10 tothe highheat chamber 11 so that the work is transferred from one chamberto the other chamber with a minimum loss of heat in the work itself.Furthermore, by interlocking the circuits as described, it will beobserved that the end doors are open for a minimum length of time sothat the inrush of cold air into the preheat and highheat chambers isminimized.

Inasmuch as the master timer 232 will be set for different periods oftime corresponding to the size of the work and nature of the heattreatment, it will be apparent that the master timer will time out andthat the contacts 233 will close under some conditions of operation whenthe roll motor 30 is oscillating the rolls in the reverse direction.Should the contacts 233 of the timer 232 close when the motor 30 isrotating in the reverse direction, it will be seen that the contacts 551of the limit switch LSK will be in their open position, so that anenergizing circuit may not be completed for the raise direction switch552 of the end doors. The motor 30 will continue to operate the rollsfor the reverse direction of rotation until the limit switch LSK isoperated to reverse the direction of rotation. As soon as the roll motor30 is operated through the predetermined angle in the forward direction,the contacts 550 and 551 of the limit switch LSK will be operated totheir closed positions as before. The energizing circuit for the raisedirection switch 552 of the end doors is thereby completed so that theend door motor 32 immediately operates to raise the end doors. Thesequence relay L3 is immediately operated to its unlatched position byreason of the completion of the energizing circuit for its trip coil565. The roll motor 30 is thereby deenergized; the contactor 501 isoperated to its open position, while the accelerating relay 226 isenergized preparatory for the speed operation of the roll motor. Thehigh speed operation of the motor 30 is accomplished by the completionof the circuits described above. It will be remembered that the highspeed operation is initiated by the closing of the end door limit switchcontacts 573, which contacts complete an energizing circuit for theforward direction switch 269. It should again be observed that byinterlocking the circuits as described, the end doors are not raiseduntil the rollers and consequently the load of material, occupy adesired position in readiness for the high speed transfer of the workfrom the preheat chamber to the highheat chamber. Furthermore, thisinterlocking insures that the charges of work in each heating chamberwill occupy the same relative positions with respect to their end doorsfor each successive change introduced into the preheat chamber.

Continuing with the operation, as the charge of work 63 approaches itsfinal position in the highheat chamber, it will be remembered that thebumper switch B1 located at the end of the highheat chamber is inreadiness for operation by the charge of work 63. As soon as the leadingends of the work 63 strike the operating lever 88 of this bumper switch,the switch is operated to close its contacts. An energizing circuit forthe operating coil of the relay 372 is thereby completed. This circuitmay be traced from the supply line 252, by conductor 590, contacts ofthe bumper switch Bl, conductor 591, operating coil of the relay 372 andby conductor 285 to the other supply line 253. The relay 372 is operatedto open its contacts 371 and to close its contacts 593 and 594. It willbe observed that the opening of the contacts 371 immediately deenergizesthe forward direction switch 269, which switch is operated to its openposition. Inasmuch as the contacts 268 operated with t e directionswitch 269 are closed, as this switch opens, to energize theaccelerating relay 226, it will be observed that the acceleratingcontactors 495, 496 and 588 are deenergized. The result is that theseries resistances 497, 498 and 500 are connected in series with thearmature circuit of the motor 30. Coincident with the closing of thecontacts 268, the contacts 595 operated with the direction switch 269are closed to connect the operating coil 596 of the contactor 597directly across the armature of the motor 30 and the series resistances497, 498 and 500. It will be remembered that the motor field winding 534is separately excited so that as soon as the direction switch operatesto deenergize the armature of the motor 30, the motor begins to act as agenerator and the resulting electromotive force applied to the operatingcoil 596 of the contactor 597 causes this contactor to be operated toits closed position. A dynamic braking circuit is thereby establishedthrough the resistance ation as determined by the dynamic braking isfurther increased by reason of the closing of the field relay 536, whichit will be observed will have voltage applied to it due to the potentialdifference existing across the series resistances 497, 498 and 500. Themotor 30 is thereby quickly brought to a standstill with the load 63 ofsteel bars at rest within the highheat chamber 11.

The next step in the sequence of operation is to close the end doors.This is accomplished by the closing of the contacts 593 of the relay 372which serves to complete the energizing circuit for the loweringdirection switch 381 of the end door motor 32. This circuit may betraced from the supply line 252 by conductor 601 and 602, contacts 593of the relay 372, contacts 380 of the relay 374, conductor 603, contacts574 of the limit switch LSD, conductor 605, contacts 606 of the bumperswitch B2, conductor 607, interlock contacts 608 of the direction switch552, operating coil 609 of the lowering direction switch 381 and byconductors 323 and 285 to the other supply line 253. The directionswitch 381 is thereupon closed to energize the motor 32 in a directionto lower the end doors.

To insure the continuance of the desired cycle of operations shouldthere be a power failure at this point in the operation of the furnace,the sequence relay L4 is operated and latched into position due to theclosing of the contacts 617 operated with the direction switch 381. Theenergizing circuit thereby completed may be traced from the supply line252 by conductor 615, operating coil of the sequence relay L4, conductor616, contacts 617 operated with the direction switch 381, and byconductors 323 and 285 to the other supply line 253. With the sequencerelay L4 in its latched-in position, it will be seen that its contacts614 are closed to establish a shunt connection around the contacts 593of the relay 372 and the contacts 380 of the relay 374.

As soon as the end doors are lowered the end door limit switch LSDoperates to open its contacts 571, 573 and 574, while its contacts 344,557 and 575 are closed. The closing of the contacts 575 energizes thetrip coil 620 of the sequence relay L4 through a circuit which may betraced from the supply line 252 by conductor 615, trip coil 620,contacts 575 of the limit switch LSD, and by conductors 621, 323 and 285to the other supply line 253. The opening of the contacts 574 of thelimit switch LSD interrupts the energizing circuit to the loweringdirection switch 381 which immediately operates to its open positionthereby deenergizing the end-door motor 32. The closing of the contacts344 of LSD completes the energizing circuit for the master timer 232which timer begins a new timing operation.

The contacts 577 and 578 of the end door limit switch LSD are soarranged that both of these contacts are closed only as the end doorsare lowered to their lower limit. The function of the contacts 577 and578 is, therefore, to give an indication that the end doors have beenhoisted 598. The rate of decelerto their upper positions and are ontheir way down to their lower limit position. At this point in the cyclewith both contacts closed, an energizing circuit for the trip coil 627of the sequence relay L5 may be traced from the supply line 252 byconductor 628, contacts 577 of the limit switch LSD, contacts 578 of thelimit switch LSD, trip coil 627, and by conductors 629, 265 and 259 tothe other supply line 253. The sequence relay L5 is thereupon operatedto open its contacts 373 and to close its contacts 370. The opening ofthe former contact serves to deenergize the relay 374 which is thereuponoperated to open its contacts 378 and 380. The closing of the contacts370 serves partially to complete an energizing circuit for the forwarddirection switch 269. It will be observed that the contacts 370 areconnected so as to by-pass the contacts 371 of the relay 372, whichrelay will remain energized by reason of the energizing circuitcompleted for its operating coil by the bumper switch B1.

It will be remembered that this bumper switch was operated by thearrival of the charge 63 of steel bars within the high heat chamber andthe closing of its contacts causes the energization of the relay 372.When this relay was operated an indication was obtained that the chargeof work had been entirely transferred from the preheat chamber 10 to thehighheat chamber 11. A circuit was thereby established for theup-direction switch 385 of the lever motor 81 by the closing of thecontacts 594 of the relay 372, so that the sequence described above forplacing a charge of work in the preheat chamber is again initiated. Theenergizing circuit for the up-direction switch 385 may be traced fromthe supply line 252, by contacts 388 of the bumper switch B2, contacts387 of the side door limit switch LSB2, contacts 388 of the cam limitswitch LSA, conductors 630 and 631, contacts 378 of the relay 374,contacts 594 of the relay 372, conductors 632 and 633, operating coil389 of the direction switch 385, interlock contacts 391 of the directionswitch 382, and by conductors 393 and 259 to the other supply line 253.The direction switch 385 is thereupon operated to its closed position toenergize the lever motor 81 in a direction to raise the charging fork43. The closing of the contacts 634 operated with the direction switch385 serves to complete an energizing circuit for the sequence relay L1,which circuit may be traced from the supply line 252 by conductor 454,contacts 634, conductor 635, operating coil of the sequence relay L1 andby conductors 383 and 259 to the other supply line 253. The

sequence relay L1 is thereupon latched into position with its contacts384 closed to complete a holding circuit for the up-direction switch385. This circuit may be traced from the supply line 252, by contacts386 of the bumper switch B2, contacts 387 of the side door limit switchLSB2, contacts 388 of the limit switch LSA, contacts 384 of the sequencerelay L1, operating coil 389 of the direction switch 385, interlockcontacts 391, and by conductors 393 and 259 to the other supply line253. It will therefore be observed that the function of the sequencerelay L1 for this part of the sequence of operation is to preventinterruption of the energizing circuit for the direction switch 385 incase of power failure, and also to insure that the lever motor 81 isenergized a suflicient length of time to raise the charging fork 43.This provision is necessary, inasmuch as it will be remembered that assoon as the sequence relay L5 is operated to its unlatched position withits contacts 373 open the relay 374 is deenergized. The contacts 3'78 ofthe relay 374, it will be remembered, form a part of the energizingcircuit which initiated the operation of the up-direction switch 385.

The closing of the contacts 399 operated with the up-direction switch385 serves to complete an energizing circuit for the sequence relay L6in the same manner as described in the initial operation of theup-direction switch. The sequence relay L6 is thereupon operated to itslatched-in position, partially completing by means of the contacts 405the energizing circuit for the in-direction switch 282 of the carriagemotor. As soon as the motor 81 has raised the levers to their upperposition in readiness for the placing of the charge 62 of steel barsinto the preheat chamber 10, the contacts 388 of the limit switch LSAare operated to their open position to deenergize the direction switch385 which in turn deenergizes the motor 81. At the same time thecontacts 409 and 410 of the limit switch LSA are operated to theirclosed positions, while the contacts 407 and 408 are operated to theiropen positions. The function of the limit switch contacts 409 isthe sameas described above and serves to complete the energizing circuit for thedirection switch 412 of the side door motor. This direction switch,thereupon closes to energize the motor 38 in a direction to raise theside door. As soon asthe side door is hoisted to its upper position thecontracts 4l4 of the track limit switch LSBI are operated to their openposition to deenergize the direction switch 412 which in turndeenergizes the side motor 38. At the same time the contacts 422 of thelimit switch LSBl are operated to their closed position to complete anenergizing circuit for the direction switch 282 for the carriage motor97. The carriage motor 9'7 is thereby energized in a direction to movethe charging fork 43 and the carriage towards the preheat chamber. Theaccelerating relay 227 again functions to energize the acceleratingcontactor 431 so that the motor is accelerated as described above. Asthe charging fork and carriage approach the limit of their travel thecarriage limit switch LSC operates to close its contacts 43'! and 438while its contacts 426 and 436 are operated to their open positions. Theopening of the contacts 426, it will be observed, deenergizes thedirection switch 282. The closing of the contacts 437 of the limitswitch LSC completes the energizing circuit for the down-directionswitch 382 of the lever motor 81. As before, when this direction switchis closed. the contacts 456 operated with it are closed to complete anenergizing circuit for the trip coil 457 of the sequence relay L6, whichrelay is thereupon operated to its unlatched position, with its contacts406 closed, partially to complete an energizing circuit for theout-direction switch 280 of the carriage motor 9'7.

It will be observed that the contacts 453 operated with the lever motordirection switch 382 are closed to complete an energizing circuit forthe trip coil 452 of the sequence relay L1. This circuit may be tracedfrom the supply line 252 by conductor 454, trip coil 452. contacts 453of the direction switch 382, and by conductors 455 and 259 to the othersupply line 253. The sequence relay L1 is thereupon operated to itsunlatched position.

As the lever motor 81 lowers the charging fork 43 it will be observedthat the charge 62 of steel bars is placed upon the roll table withinthe preheat chamber, while the third charge of steel bars which has beenplaced on the charging fork is transferred to the forward position whichwas formerly occupied by the charge 62. As the charging fork reaches itslower position the cam limit switch LSA again functions to close itscontacts 388, 407 and 408, while its contacts 409, 410 are opened. Theopening of the contacts 410 of the limit switch LSA serves to deenergizethe down direction switch 382 of the lever motor. The closing of thecontacts 408 of the limit switch LSA completes an energizing circuit forthe outdirection switch 280 of the carriage motor 9'7, as has beendescribed above. The motor 9'7 thereupon functions to drive the carriageand the charging fork from the preheat chamber. As the carriageapproaches its outer limit of travel, the carriage limit switch LSCoperates to open its contacts 437 and 438, and to close its contacts 426and 436. The opening of the contacts 438 interrupts the energizingcircuit to the direction switch 280 which is thereupon operated to itsopen position to deenergize the carriage motor 97 and to establish adynamic braking circuit through the braking resistor 440 so that thecarriage is quickly brought to a standstill.

The closing of the contacts 436 of the limit switch LSC completes anenergizing circuit for the lowering direction switch 3'79 of the sidedoor motor 38. This motor is thereupon energized in a direction to lowerthe side door. The contacts 480 operated with this switch are closed tocomplete an energizing circuit for the sequence relay L3. This sequencerelay is thereupon operated and latched into its closed position withits contacts 487 closed and its contacts 267 open. As soon as the sidedoor 39 reaches its lower position the track limit switch LSB2 operatesto close its contacts 387 and to open its contacts 4'73, the latter ofwhich serves to deenergize the lower-direction switch 3'79.

Inasmuch as the oscillation of the rollers is next in order it will beseen that the closing of the contacts 487 of the sequence relay L3serves to complete an energizing circuit for the contactor 501 whichcontactor is thereby operated to its closed position to establish theshunt connection through the resistance 490 for the armature of themotor 30. The contacts 514 operated with the contactor 501 are closed tocomplete the energizing circuit for the clutch operating coil 515. Theclutch is thereupon operated to connect the limit switch LSK with theroll motor 30. A circuit is also completed by reason of the closing ofthe contact 487 of the sequence relay L3 for the forward directionswitch 269 of the roll motor. This circuit may be traced from the supplyline 252 by conductor 502, contacts 487 of the sequence relay L3,conductor 522, contacts of the timing relay TF, conductor 524, contacts525 of the pushbutton station 526, conductor 527, contacts 528 of thelimit switch LSK, contacts 362 of the relay 301, contacts 3'70 of thesequence relay L5, conductor 582, operating coil 530 of the directionswitch 269, interlocking contacts 531 of the direction switch 532, andby conductors 533, 265 and 259 to the other supply line 253.

As described above, the opening of the contacts 267 of the sequencerelay L3 serves to de energize the accelerating contactors 495, 496 and588, so that when the direction switch 269 is closed to energize theroll motor 30, the motor functions to drive the rolls at very low speed.As before, the field accelerating relay 536 operates to short circuitthe field resistance 535 to further insure low speed operation of theroll motor 30.

The limit switch LSK thereafter functions to I of the roll motor.

control the energization of the roll motor 30 in conjunction with thetiming relays TF and TR so that the charge 62 in the high heat chamberand charge 63 now in the preheat chamber are reciprocated to and fro forthe reasons and purposes that I have already explained.

It will be remembered that as soon as the contacts 344 of the end doorlimit switch LSD were closed, the master timer 232 was again set intooperation. As soon as the expiration of the time interval, however, themaster timer 232 again times out to close its contacts 233. The rollermotor 30, however, continues the reciprocation of the work in theheating chamber until the predetermined point in the forward directionof rotation is reached at which point the contacts 550 and 551 of thelimit switch LSK are operated to their closed positions. When thisoccurs, it will be observed that the contacts 551 serve to complete anenergizing circuit for the raise direction switch 552 of the end doors,this circuit being traced as before from the supply line 252 byconductor 554, contacts 551 of the limit switch LSK, conductor 555,contacts 233 of the master timer, conductors 556 and 837, contacts 557of the end door limit switch LSD, conductor 558, operating coil 559 ofthe raise direction switch 552, interlock contacts 560 of the lowerdirection switch 381 and by conductors 323 and 285 to the other supplyline 253. Consequent to the closing of the raise direction switch 552,the end door motor 32 is energized in a direction to raise the enddoors.

The closing of the contacts 562 operated with the direction switch 552again serves to complete an energizing circuit for the trip coil 565 ofthe sequence relay L3, this circuit as before being dependent upon theclosing of the contacts 550 of the limit switch LSK and the closing ofthe contacts 562 of the direction switch 552. The sequence relay L3 isthereupon operated to its unlatched position with its contacts 487 openand its contacts 267 closed. The former contacts as before, serve todeenergize the contactor 501 which is operated to its open position,while the contacts 514 operated with this contactor are open todeenergize the clutch operating coil 515. The opening of these contacts,it will be remembered, also serves to deenergize the direction switch269 which immediately operates to its open position thereby closing itscontacts 268 operated with this switch to complete the circuit partiallycompleted by the contacts 267 of the sequence relay L3 for theaccelerating relay 226, which relay is operated to open its contacts.

Consequent to the arrival of the end doors in their upper positions, theend door limit switch LSD operates to close its contacts 571, 573 and574, while its contacts 344, 557 and 575 are operated to their openpositions. The opening of the contacts 557 deenergizes the raisedirection switch 552 of the end door motor 32, while the closing of thecontacts 573 serves to complete an energizing circuit for the forwardswitch 269 This circuit may be traced from the supply line 252, byconductor 554, contacts 551 of the limit switch LSK, contacts 573 of theend door limit switch LSD, conductor 580, contacts 362 of the relay 363,contacts 370 of the sequence relay L5, conductor 582, operating coil 530of the direction 269, interlock contacts 531 of the direction switch532, and by conductors 533, 265 and 259 to the other supply line 253.Following the closing of the direction switch 269 the roll motor 30 isaccelerated to its full speed in the manner described above when thecharge 63 was transferred from the preheat chamber to the high heatchamber. The rotation of the motor 30 in the forward direction nowserves to transport the charge 63 of steel bars to the runout table,while the charge 62 is transferred to the high heat chamber.

As the leading end of the steel bars 63 passes through the end door 33of the high heat chamber, the bumper switch B2 will be operated to openits contacts 386 and 606. The opening of the contacts 386, it will beobserved, interrupts the supply circuit to the crane hoisting motor 37,normally traced by the conductor 640 in order that the crane may not beoperated while the work is on its way from the high heat chamber to therunout table. The opening of these contacts also interrupts theenergizing circuit for the up direction switch 385 of the lever motor sothat the levers may not be operated while the charge of steel bars inthe preheat chamber is being transported to the high heat chamber. Theopening of the contacts 606 of the bumper switch B2 serves to interruptthe lowering circuit of the direction switch 381 of the end doors sothat the end doors may not be lowered until the work has been entirelytransported from its former position to its new position, that is tosay, until the charge 63 has been transferred to the run-out table whilethe charge 62 has been transferred to the high heat chamber. As soon asthe trailing ends of the steel bars 63 leave the operating lever of thebumper switch B2, this limit switch is again operated to close itscontacts 386 and 606.

It will be remembered that the bumper switch B3 located at the end ofthe run-out table is arranged to be operated by the leading ends of thework as it arrives in position on the runout table. As soon as theleading ends of the work arrive in position the contacts of the bumperswitch B3 are thereby closed to complete an energizing circuit for theoperating coil of the relay 361. This circuit may be traced from thesupply line 252 by conductor 641, contacts 01' the bumper switch B3,conductor 642, operating coil of the relay 301, and by conductors 643and 285 to the other supply line 253. The relay 301 thereupon operatesto open its contacts 300 and 362 and to close its contacts 644, 646 and647, the opening of the contacts 362 serving to interrupt the energizingcircuit to the direction switch 269. As explained above, the opening ofthe direction switch 269 serves to complete an energizing circuit bymeans of its contacts 268 for the accelerating relay 226, which relayoperates to open its contacts so that the accelerating contactors 495,496 and 588 are deenergized and operated to their open position tore-insert the series resistances 497, 498 and 500 in the armaturecircuit of the motor 30. The contactor 597 is operated to its closedposition by reason of the potential difference existing across thearmature and the series resistances 497, 498 and 500 of the motor 30. Adynamic braking circuit through the resistor 598 is thereby establishedand the motor 30 will be braked to a standstill. The field relay 536again functions to increase the excitation produced by the field winding534 on the motor 30 thereby increasing the dvnamic braking effort of themotor 30.

The closing of the contacts 646 of the relay 301 serves to complete anenergizing circuit for the up-direction switch 385 of the lever motor.This circuit may be traced from the supply line 252 by contacts 386 ofthe bumper switch B2, contacts 387 of the side door track limit switchLSH2, contacts 388 of the limit switch LSA conductor 630, contacts 646of the relay 301, conductor 633, operating coil 389 of the up-directionswitch 385, interlock contacts 391 of the direction switch 382, and byconductors 393 and 259 to the other supply line 253. The up-directionswitch 385 is thereby closed to energize the motor 81 in a direction toraise the charging fork 43. The closing of the contacts 634 operatedwith the direction switch 385 again serves to complete an energizingcircuit for the sequence relay L1. This relay is operated to its latchedin position with its contacts 384 closed to maintain the energizingcircuit for the up-direction switch 385 until this direction switch isdeenergized by the opening of the contacts 388 of the lever limit switchLSA. The closing of the contacts 399 operated with the direction switch385 again serves to complete an energizing circuit for the sequencerelay L6 which is operated to its latched in position partially tocomplete an energizing circuit for the in-direction switch 282 of thecarriage motor 97. The contacts 409 of the lever limit switch LSA areagain closed as soon as the charging fork 43 has been raised to itsupper position to complete an energizing circuit for the raise-directionswitch 412 of the side door motor 38. The energizing circuits describedand traced above are again completed so that the side door is raised toits upper position, the carriage is moved towards the preheat chamberuntil the charging fork 43 is in a position to deposit the next loadwithin the preheat chamber. The levers are operated to lower thecharging fork, the sequence relays L1 and L6 are tripped and operated totheir unlatched positions. The carriage motor 97 is energized to drivethe carriage to the preheat chamber, while the side door motor 38 isagain energized to lower the side door.

consequent to the closing of the relay 301 an energizing circuit wascompleted through its contacts 647 for the lowering direction switch 381of the end door motor 32. This circuit may be traced from the supplyline 252 by conductor 601, contacts 647 of the relay 301, contacts 574of the end door limit switch LSD, conductor 605, contacts 606 of thebumper switch B2, conductor 60'7, interlock contacts 608 of the raisedirection switch 552, operating coil 609 of the lower direction switch381, and by conductors 323 and 285 to the other supply line 253.

It will therefore be observed that the end doors are lowered just assoon as the steel bars have arrived in position on the run-out table. Ineach case provision is made so that the end doors are lowered at thesame time that the side door is being raised. This interlocking of thecircuit serves to minimize the loss of heat due to the hoisting of theside door and of the end doors. For example if both the side door 39 andthe end door 35 of the preheat chamber were in their full open positionsat the same time, it will be seen that a substantial loss of heat mighttake place due to a draft which might result through the preheat chamber10.

The opening of the contacts 300 and the closing of the contacts 644 ofthe relay 301 initiate the operation of the hoisting motor 37 so thatthe load 63 which has arrived on the run-out table is immediatelytransported to the quenching tank. It will be remembered that theenergizing circuit for the accelerating contactors 298 and 309 of thehoisting motor 37 were traced through the contacts 300 of the relay 301.Therefore, as soon as the relay 301 operates to open its contacts 300the contactors 298 and 309 were operated to their open positions, due tothe interruption of their energizing circuits.

The closing of the contacts 644 of the relay 301 serves to complete anenergizing circuit for the sequence relay L7. This circuit may be tracedfrom the supply line 252 by conductor 299, contacts 644 of the relay301, conductor 645, operating coil 648 of the sequence relay L7, and byconductors 404 and 259 to the other supply line 253. The sequence relayL7 is thereupon operated to its latched-in position with its contacts655 closed to complete an energizing circuit for the hoisting relay 290.This circuit may be traced from the supply line 252 by contacts 386 ofthe bumper switch B2, conductor 640, contacts 655 of the sequence relayL7, contacts of the track type limit switch LSH2, conductor 658,contacts 659 of the limit switch LST operated by the trolley motor 48,conductor 660, interlock contacts 662 of the lowering relay 293,operating coil 663 of the hoisting relay 290, and by conductor 665 tothe other supply line 253. The hoisting relay 290 is thereupon operatedto open its contacts 303 and 289 while it closes its contacts 666, 667,668 and 670. The opening of the contacts 303 serves to prevent thesubsequent energization of the accelerating contactors 298 and 309through the circuit completed by the contacts 644 of the relay 301. Theopening of the contacts 289 of the hoisting relay serves to deenergizethe field accelerating contactor 287, which contactor is therebyoperated to its open position. The closing of the contacts 667 of thehoisting relay 290 serves to complete an energizing circuit for thefield accelerating contactor 312 which circuit may be traced from thesupply line 252 by conductors 274, 276 and 314, contacts 667 of thehoisting relay 290, conductor 672, operating coil 316 of the contactor312, and by conductor 317 to the other supply line 253. The closing ofthe contacts 666 of the hoisting relay 290 completes the energizingcircuit of the time closing relay TR2. This circuit may be traced fromthe supply line 252, by conductors 274, 276, 798, contacts 666 of thehoisting relay, operating coil of the relay TR2 and by conductor 665 tothe other supply line 253.

The closing of the contacts 670 of the hoisting relay serves to completean energizing circuit for the hoisting direction switch 676. Thiscircuit may be traced from the supply line 252 by contacts 386 of thebumper switch B2, conductor 640, contacts 655 of the sequence relay L7,contacts of the track type limit switch LSH2, conductor 658, contacts659 of the trolley limit switch LST, conductor 660, interlock contacts662 of the lowering relay 293, contacts 670 of the hoisting relay 290,conductor 677, operating coil 678 of the hoisting direction switch 676,and by conductor 665 to the other supply line 253. The hoistingdirection switch 676 is thereby closed to energize the hoisting motor 37through a circuit which may be traced from thepositive source of supply,hoisting direction switch 676, series resistances 680 and 681, thearmature of the hoisting motor 37, series field winding 682, seriesbrake coil 683, contacts of the field accelerating contactor 312, (whichcontacts by-pass the resistances 684 and 686) and by resistance 687 tothe negative source of supply.

When the hoisting direction switch 676 closed, the contacts 688 operatedwith this switch were closed to complete an energizing circuit for the

